Method of manufacturing the focusing grids of color television tubes

ABSTRACT

A method of manufacturing focusing grids for color television tubes, consisting in first producing a sheet of wires having the desired accuracy in terms of pitch and flatness, on a prismatic drum the corners of which are constituted by precision screws in the threads of which the wires are laid. The wires are then preliminary fixed to channel irons carried by the side members of a precision frame. A substantial economy is achieved by using the same frame for manufacturing a great number of grids. Only the channel iron need to be changed.

Qniied States Patent 921 Inventor mm M-Ill 211113.213 11/1957 (tamer313178 Plight-x 1130.757 4/l964 Schcllack 140/7115 TI Appl in 795973357,45) l2/l967 (ahen l40/7l S 22 Filed 1-. 28. I969 3.489366 1/1970Bradum 1 313/283 X 4 Pnemcd Primary Examiner-John F Cam bell I Assugneeliaison-(SF p Pnom Feb I 1% Assistant Examiner-Richard Bernard Lazarus ts U w l 1 3] m Attorney Cushman Darby & (,ushman ll l LSJS m1 mzmon orMANUFACTURING ms rocusmc (nuns OF COLOUR TELEVISION 'ITBES 1 5 win;3hhs' on m ABSTRACT: A method of manufacturing focusing grids for l Us l29/2514, color television tubes, consisting in first producing a sheetof 29/2 i I40 1 140/71 5 wires having the desired accuracy in terms ofpitch and flat- 1 I 1 Int, Cl. [101 9/00 mass on a prismatic drum thecorners of which are constituted l 1 Field Search. 140/71 by precisionscrews in the threads of which the wires are laidv 7161905 H 2. I3 25I4. 2 I5. 25 17 The wires are then preliminary fixed to channel ironscarried g by the side members of a precision frame. h I Cited Asubstantial economy is achieved by using the same frame UNITED STATES PATENTS for manufacturing a great number of grids Only the channel 2 H0186IO/1957 pru zyn l |4OHL5X iron needtobechangedi l YD The presentinvention relates to a method of manufacturing the focusing grids ofcolor television tubes.

Certain kinds of color television tubes comprise a two-part envelope,namely the front wall carrying the screen and the flared envelopeportion or cone, in the neck of which the electron-guns are located. Thefocusing grid is clamped between these two parts at the time that thetube is sealed.

This grid, which is generally in the form of a flat sheet of parallelwires, must satisfy a variety of conditions relating in particular tothe mutual parallelism of the wires of which it is made, the wire pitch,that is to say the spacing between two successive wires, and the overallflatness of the grid. The tolerance in these respects is no more than afew hundredths of mm. In order to keep within these tolerances,generally the grid is produced by stretching the wires over a framewhich itself is manufactured to the said tolerances, the grid, thustensioned in position on the frame, than being located between the twosections of the tube envelope at the time of the sealing of the latter.

This method means that the cost of the finished product is high, becauseof the necessity to manufacture a precisionmachined frame for each grid.

The present invention relates to a method of manufacturing the grid,which overcomes this drawback.

According to the invention there is provided a method of manufacturingfocusing grids for color television tubes comprising the steps ofpreparing a sheet of parallel wires on the sides of a prism-shaped drum,whose edges are formed by screws of high precision whose pitch is thatof the desired grid, said wires being positioned in the threads of saidscrews, and fixing the wires of a sheet on a frame on which the gridremains until the grid is clamped between the front wall and the flaredportion of the tube envelope, the same frame being thus used for forminga plurality of grids.

For a better understanding of the invention and to show how the same maybe carried into effect reference will be made to the drawingaccompanying the ensuing description and in which:

FIG. 1 schematically illustrates, in section, the relative dispositionof the elements of a color television tube concerned with the invention;

FIG. 2 shows in perspective a grid stretched on its frame;

FIG. 3 is a perspective view of a color television tube ready forsealing;

FIG. 4 is a schematic view, in section, of an arrangement for themanufacture of color television tube grids, in accordance with theinvention; and

FIG. 5 is a sectional view of the frame-grid assembly, as it appearsafter the attachment of the grid to the frame, in the arrangement ofFIG.4.

In all these figures, similar reference symbols designate similarelements.

FIG. 1 schematically illustrates, in section, the front wall F of thetube envelope carrying the screen E, its flared portion C, in the neck cof which there are located the electron-guns CE. A grid G is clampedbetween the two parts of the tube envelope. This grid is shown inperspective in FIG. 2. It is made up of parallel wires 3, stretched on aframe D.

In FIG. 3, the aforementioned elements can again be seen, inperspective, the tube being ready for sealing. Stops I0 keep the grid inthe desired position in relation to the front wall F,

during the sealing operation.

FIG. 4 schematically illustrates, in section normally to its axis 1 adrum 1 in the shape of a regular prism, the edges of which areconstituted by precision screws 2 and which is associated with a reel 3,the axis 3 of which is parallel to the screws 2. The axis 3' of the reelis fixed to the same frame as the drum 1. I

The drum I is made to rotate about its axis 1' in the direction of thearrow so that it picks up on the screws 2 a sheet of wires g running offthe reel 3, the wires 3 seating in the threads of the screws 2. The drumsides are larger than the frame D.

The drum 1 is then halted and opposite each of its faces, i.e. betweentwo successive screws 2, inside the drum 1, frames D are brought inposition at a distance of some few tenths of mm. from the sheets ofwires g.

FIG. 5 illustrates in section an embodiment of the frame D.

The side members 11 and 11 of the frame D carry removable channel irons20 and 20', enabling the same frame to serve many times.

The frame D being in position in relation to the wires 3, as shown inFIG. 5, the grid wires g are preliminarily fixed at 30 and 30' to thechannels 20, 20 respectively, by means of any suitable adhesive such asan organic resin or cement, this over the whole of their height.

The object of this preliminary fixing is to ensure correct positioningof the grid wires g during the final fixing operation which ispreferably carried out by application of a metal to each of the twochannels, using a metallizing torch such as a Shoop pistol, themetallizing being applied at 50 and 50'.

Subsequently, the grid wires g are cut at each extremity at 40 and 40',between the frame D and the screws 2. It goes without saying that priorto the cutting of the wires 3, it is necessary, in order to prevent thedestruction of the wire sheet which they form, to fix them preliminarilyat least to the frames at the adjacent faces.

This leaves a grid ready for sealing, the pitch of the grid wires beingthat of the screws 2 and its flatness being that of the faces of theprismatic drum used.

The winding of the grid wires 3 onto the drum 1 may possibly be carriedout in two stages, the odd number wires being wound on during one of thestages and the even number ones during the other.

The drum 1 may have different numbers of sides, for example between 4and 30.

Of course the invention is not limited to the embodiments described andshown which were given solely by way of example.

I claim:

1. A method of manufacturing focusing grids for color television tubescomprising the steps of preparing a sheet of parallel wires on the sidesof a prism-shaped drum, whose edges are formed by screws of highprecision whose pitch is that of the desired grid, said wires beingpositioned in the threads of said screws, preparing a frame, mounting,on two opposite side members of said frame, two removable channel irons,and fixing the wires of a sheet on said channel irons on which the gridremains until the grid is clamped between the front wall and the flaredportion of the tube envelope, the same frame being thus used for forminga plurality of grids.

2. A method as claimed in claim 1, wherein said fixing on said frame isperformed by means of a metallizing torch.

3. A method as claimed in claim 1, wherein prior to fixing said grid onsaid frame, it is preliminarily fixed by means of an adhesive.

1. A METHOD OF MANUFACTURING FOCUSING GRIDS FOR COLOR TELEVISION TUBESCOMPRISING THE STEPS OF PREPARING A SHEET OF PARALLEL WIRES ON THE SIDESOF A PRISM-SHAPED DRUM, WHOSE EDGES ARE FORMED BY SCREWS OF HIGHPRECISION WHOSE PITCH IS THAT OF THE DESIRED GRID, SAID WIRES BEINGPOSITIONED IN THE THREADS OF SAID SCREWS, PREPARING A FRAME, MOUNTING,ON TWO OPPOSITE SIDE MEMBERS OF SAID FRAME, TWO REMOVABLE CHANNEL IRONS,AND FIXING THE WIRES OF A SHEET ON SAID CHANNEL IRONS ON WHICH THE GRIDREMAINS UNTIL THE GRID IS CLAMPED BETWEEN THE FRONT WALL AND THE FLAREDPORTION OF THE TUBE ENVELOPE, THE SAME FRAME BEING THUS USED FOR FORMINGA PLURALITY OF GRIDS.
 2. A method as claimed in claim 1, wherein saidfixing on said fRame is performed by means of a metallizing torch.
 3. Amethod as claimed in claim 1, wherein prior to fixing said grid on saidframe, it is preliminarily fixed by means of an adhesive.